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Capability Development for Assessing Perturbations to the Global Carbon Cycle Due to Impact-Generated Wildfires, 15-9320

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Principal Investigator
Daniel D. Durda

Inclusive Dates: 05/31/02 - 09/30/02

Background - One of the largest disruptions of the global carbon cycle occurred 65 million years ago following the K/T boundary Chicxulub impact event, widely recognized as the event that precipitated the extinction of the dinosaurs and some 75 percent or more of other animal and plant species on Earth at that time. Computer simulations of the impact event, in which an approximately 10-kilometer-diameter asteroid or comet struck what is now the Yucatan peninsula at several tens of kilometers per second, indicate that it vaporized a large amount of carbon-bearing rock and injected 350 to 3,500 billion tons of carbon dioxide into the stratosphere. In addition, widespread wildfires were ignited by atmospheric heating when impact ejecta were blasted well clear of the atmosphere and then began to re-enter and reaccrete to Earth minutes to hours later.

Approach - The objectives of this research effort were to:

  • Conduct preliminary field work to resample a K/T boundary section in southern Colorado for carbon analysis, so that SwRI can demonstrate its ability to search for evidence of wildfires and to determine if ecosystem changes following the Chicxulub impact varied with the type of environment (forest versus swamp, and so on),
  • Develop the Interactive Data Language (IDL) interpretation and visualization tools that will enable the research team to translate the results of CTH hydrocode simulations of large impact events into a format usable by the team's ejecta reaccretion code, and
  • Incorporate the results of a CTH simulation of the Chicxulub impact as input initial conditions to the team's numerical model that tracks the trajectories of re-entering impact ejecta material and calculates atmospheric heating.

Accomplishments - Geologic Field Work From 14 -17 July 2002: Team members traveled to the Raton Basin in southern Colorado, near the city of Trinidad, to collect a new suite of K/T boundary sediments. The goal was to collect samples that would allow the team to determine how various plant ecosystems recovered after the K/T boundary Chicxulub impact event. Samples for this project were collected from three of the better known K/T boundary sites in the Raton Basin (Clear Creek North, Madrid, and Starkville South). Ninety-four samples were collected and are being prepared in a team member's laboratory for molecular and isotopic carbon analysis.

CTH Output Visualization: For this task the team proposed to develop a set of IDL software tools to 1) interpret the results of the team's CTH hydrocode models of the Chicxulub impact event (and others), and 2) utilize those results in determining the initial launch conditions for the suite of tracer particles in subsequent dynamical models that calculate reaccretion and atmospheric heating. The team used instead Sandia's graphics programs cthplt and popx11 to generate plots for interpretation of simulation results.

CTH Output Handoff to Dynamical Reaccretion Code Work to translate the CTH output into a format readable by the team's dynamical ejecta reaccretion code is still underway. As anticipated, the addition of multiple geologic materials simultaneously within a single model added a new level of complexity to the problem, but the benefit of this scheme over SwRI's previous ejecta reaccretion studies is that it allows a rigorous treatment of the impact physics, so that realistic ejecta mass and velocity fields are established early in the cratering process.

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